365 - 390 Valve Cover Gaskets,

[Grant Owen]

Does any one know if anyone makes a decent thick gasket seems as though the day has gone when you could put them on nip them up & never have a leak. Please do not say use sealer. If you can think of anyone that does please let me know , before I waste my time reproducing them , same goes for the Fuel filter Gasket does anyone make a decent cork gasket .

[Roger Zimmermann]

Did you try the valve cover gaskets from Best Gasket? They are cork, thick, if you are ordering the right ones. The late 390 engines are using a thin gasket, the earlier ones a thicker one. I'm using a sealer to the valve cover not to seal the gasket but just to be sure that the gasket is not slipping away in the corners.
Don't torque the screws too much and verify first if your valve covers are not distorded.

[Grant Owen]

Roger I have Felpro & Best Gaskets , they are both thinner than they should be . I had leaking covers on a 1960 using Best gaskets so I used my last set of thick gaskets probably about 15 years old & the problem solved. I have a set of the early 57 & earlier gaskets that are also old they are 1/4" thick the new ones don't even come close to being that thick.

[fishnjim]

Been there done that.   I had to shave a few 32nds off the valve cover in 3 places on one side where it goes over the head bosses to use the modern gaskets.   They prevent the cover from going down to new height.   
I bought several different sets and could not find the proper thickness cut gaskets.   You'd probably have to cut your own.   I bought thick rubber but didn't use as this worked out better for next time.   A little gasket sealer on the cover won't hurt.
You could use two but would have to use sealer between and they won't be as tight/may leak.

[Roger Zimmermann]

Today, I measured the gaskets I have, the thicker ones. They are 4.7 mm or 0.185". With them, I have no problem with my 56 and 57 cars.

[Grant Owen]

Roger , the pre early 57 Gaskets I have the old ones are 6.35mm 1/4" the new ones are 3.9mm (felpro).

[Roger Zimmermann]

3.9 mm? I did compare yesterday the earlier and late gaskets, but did not measure the thinner ones. To me, the "thick" gaskets from Felpro are the late thin ones; on earlier engines, there could be some interference between the block and valve covers, preventing a good sealing.
I used to buy Felpro gaskets, now I'm only buying the ones from Best Gasket because Terrill Machine is just selling them.